Two sizes are available; 3.5 ml (standard) and 1.5 ml (semi-micro). All cuvettes have a 10 mm path length and are 45 mm high. Internal width of the semi-micro size is 4 mm. We also have cuvette caps made from polyethylene which are easy to insert and remove. The caps seal liquid tight, suitable for mixing and storage. Sold in lots of 500.